The human body's ability to maintain homeostasis is due in part due to respiratory functions controlled by the brain and associated feedback systems. In maintaining homeostasis, respiratory functions typically alter both blood oxygen saturation and carbon dioxide partial pressures.
Certain pathological conditions such as circulation delay in heart failure patients may lead to instability in the respiratory feedback systems. Circulatory delay is believed to cause phase shift or time delay in the inherent blood gas sensing feedback loop. One manifestation of this is resulting breathing disorders including periodic breathing, Cheyne-Stokes, and apnea (predominantly central sleep apnea (CSA)). Cheyne-Stokes respiration is believed to occur in part because of this circulatory delay and perceived drop in SaO2 levels. Central apnea, and, in some cases obstructive apnea, is believed to occur in part due to a drop in partial pressure of CO2 following a Cheyne-Stokes hyperventilation pattern. Other conditions such as congestive heart failure (CHF) may be able to derive a benefit by an increase in the partial pressure of O2 above that which is normally maintained.
Mechanical ventilators have been used to take over breathing to ensure adequate oxygen levels in patients who cannot sufficiently breath on their own or who stop breathing at night during apnea events. Mechanical ventilators control the inflow and egress of respiratory gasses by controlling combinations of flow, pressure and/or volume. The ventilator delivers an inspiration via positive pressure delivered into the trachea and lungs and can control exhalation by manipulating pressure and flow.
Diaphragm stimulation has been used to create respiration in patients who cannot breath on their own and has been suggested to stimulate breathing when apnea occurs. Diaphragmatic stimulation has generally been used to control inspiration via contraction of the diaphragm muscle which creates negative intra-thoracic pressure resulting in inspiration. Exhalation has generally been a passive process driven by lung and thoracic compliance.
The ventilators and proposed diaphragm stimulation have not addressed the causes of breathing disorders, but rather have been limited to supplementing breathing when breathing is insufficient or not present.